Owing to the increasing popularity of digital cameras and digital video cameras in recent years, it is becoming increasingly common for an individual to possess a large quantity of digital image data. If the quantity of image data possessed thus becomes very large, the method used to retrieve desired image data from this image data becomes important. For example, there is need for a method used when it is desired to retrieve from digital image data only images in which the faces of persons appear or only images in which the face of a specific individual appears.
By performing retrieval in this manner, it becomes possible to execute processing through which digital image data in which a specific individual appears is placed in a specific folder or through which only the face area is cut from the image data and combined with other digital image data.
A technique for retrieving the area of the face of an individual from image data that contains the face of the individual includes pre-registering data, which characterizes the face of the individual, as reference face data in order to retrieve the specific individual, compare the registered reference face data with image data that is the object of the search, and retrieve an image area having face data that resembles the reference face data (see the specification of Japanese Patent Application Laid-Open No. 2002-183734).
In the image retrieval described above, however, it is necessary to register the reference face data in advance. As will be described below, such image retrieval does not lend itself to consumer products because the operation involved is troublesome.
Specifically, when face data serving as a reference for the object of a search is registered, the image file containing the face desired to be registered is designated, the image data of this image file is displayed and the face to serve as the reference is registered by designating the area of the desired face in the image. At this time feature data that characterizes the face is extracted from the image data of the face and the feature data is stored as the reference face data.
Next, when retrieval is carried out, the image file to be retrieved is designated. When this is done, the reference face data characterizing reference faces and the image data of the image file to be retrieved are compared and image data containing the face that most resembles the sought face is retrieved.
With the conventional retrieval apparatus, the operation for registering the reference face data desired to be retrieved and the operation for retrieving a face in image data are separate operations, as described above. The user seeking to perform retrieval, therefore, is required to carry out the troublesome operation of registering reference face data in advance. This does not lend itself to the users of consumer products in particular.
Further, if the face of an individual has been retrieved, the user interface that determines how the retrieved face will be shown to the user also is important.
The specification of Japanese Patent Application Laid-Open No. 10-334213 discloses an invention entitled “Image Processing Apparatus and Medium Storing Program for Controlling Image Processing Apparatus”. The disclosed invention detects a face area in digital image data containing a picture of a person by comparing color data of the image and face-recognition color data prepared in advance and displays by complementary color data in inverse video a face area having the largest area, thereby indicating to the user where the face area to be retrieved is located. Further, by touching a “SELECT” button, a face area having the next largest area is detected and this face area is displayed in inverse video.
Though the specification of Japanese Patent Application Laid-Open No. 10-334213 discloses that a plurality of face areas in digital image data of a single image are displayed in inverse video one after another by the “SELECT” button, the specification makes no disclosure whatsoever concerning a user interface for a case where there are multiple images represented by digital image data having face areas.
Further, when retrieval of a face is actually performed by a user, generally digital image data of a plurality of images is retrieved. A problem is that a user interface for dealing with retrieved multiple images becomes necessary.